'Things are not cheap,' says dealmaker Rubenstein

Though the pace of private equity deals is picking up, finding undervalued acquisition targets is "never easy," said David Rubenstein, co-founder of The Carlyle Group.

"Things are not cheap," he said in an interview on CNBC's "Squawk Box" Tuesday.

"Right before the recession in 2007 and 2008, the average EBITA [earnings before interest, taxes and amortization] multiple for a buyout was 9.7 times." Rubenstein said. "It went as low as maybe six or seven times a couple of years after the recession."

Today, he said, the average EBITA multiple for a buyout is back at 9.7 times.

"You have to be very judicious looking for things that you can find ways to make 20 percent to 30 percent rates of return," Rubenstein said.

"Last year, there was still a much smaller [number] of global private equity deals, and deals in the United States, than in 2007 or 2008," he said, adding that "we're still only about 50 percent the dollar volume" of that period.

Rubenstein said activity is accelerating a bit because "financing is readily available ... on attractive terms."

Carlyle has more than $185 billion in assets under management from 1,550 investors in 74 countries.